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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=PL link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='color:windowtext'>Dear David and Arian,<o:p></o:p></span></p><p class=MsoNormal><span style='color:windowtext'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:windowtext'>Thank you for your quick response.<o:p></o:p></span></p><ol style='margin-top:0cm' start=1 type=1><li class=MsoListParagraph style='color:windowtext;margin-left:0cm;mso-list:l0 level1 lfo1'><span lang=EN-US>Unfortunately changing time step doesn’t help (we change form 1h to 5 min).<o:p></o:p></span></li><li class=MsoListParagraph style='color:windowtext;margin-left:0cm;mso-list:l0 level1 lfo1'><span lang=EN-US>We also try switch off internal calculation of convection coefficient on ceiling but it not help, moreover it is not solution for us as we simulate TABS. However we will switch off internal calculation of convection coefficient for windows and external walls.<o:p></o:p></span></li></ol><p class=MsoNormal><span lang=EN-US style='color:windowtext'>Do you have any other idea?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:windowtext'>Do you think that some settings in Control Cards could help (change in numerical approach)?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:windowtext'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:windowtext'>Best,<br>Karol<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:windowtext'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span style='color:windowtext;mso-fareast-language:PL'>From:</span></b><span style='color:windowtext;mso-fareast-language:PL'> David BRADLEY <> <br><b>Sent:</b> Tuesday, August 16, 2022 8:38 PM<br><b>To:</b> TRNSYS users mailing list at OneBuilding.org <trnsys-users@lists.onebuilding.org><br><b>Cc:</b> karol.bandurski@put.poznan.pl<br><b>Subject:</b> Re: [TRNSYS-users] convergence problems because of high ventilation heat flux<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p>Karol,<span style='mso-fareast-language:PL'><o:p></o:p></span></p><p> Check your assumption about the way that the inside heat transfer coefficients are being calculated on the zone surfaces. If you have allowed the convection coefficients to be internally calculated then you can end up with convergence problems inside 56, particularly on inside window surfaces and even more particularly if the glass has a high u-value.<o:p></o:p></p><p>kind regards,<o:p></o:p></p><p> David<o:p></o:p></p><p><o:p> </o:p></p><div><p class=MsoNormal>On 08/16/2022 09:50, karol.bandurski--- via TRNSYS-users wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal><span lang=EN-US>Dear Experts.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>We get convergence problem in Type 56. According to our investigation source of error is sudden increase of ventilation flow in our schedule and ventilation air temperature about 3 K lower then room air temperature.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>We would like to keep this control schedule and the same time avoid convergence problem.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>So far we have increase indoor air heat capacity in zones (five times), it help a bit.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>Do you have any other ideas what we could do?</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>Should we change something in Control Cards?</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>Best,</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>Karol </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal style='background:white'><span lang=EN-US style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:PL'>---------------------------------------------------------------------------</span><o:p></o:p></p><p class=MsoNormal style='background:white'><span lang=EN-US style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:PL'>Karol BANDURSKI Ph.D, Assistant Professor </span><o:p></o:p></p><p class=MsoNormal style='background:white'><span lang=EN style='mso-fareast-language:PL'>Faculty of Environmental and Energy Engineering </span><o:p></o:p></p><p class=MsoNormal style='background:white'><span lang=EN-US style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:PL'>Division of Heating, Air Conditioning and Air Protection </span><o:p></o:p></p><p class=MsoNormal style='background:white'><span lang=EN-US style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:PL'>Poznan University of Technology</span><o:p></o:p></p><p class=MsoNormal><span style='mso-fareast-language:PL'><a href="https://www.researchgate.net/profile/Karol_Bandurski"><span lang=EN-US style='color:blue'>https://www.researchgate.net/profile/Karol_Bandurski</span></a></span><o:p></o:p></p><p class=MsoNormal><span style='mso-fareast-language:PL'>***</span><o:p></o:p></p><p class=MsoNormal style='background:white'><span style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:PL'>dr inż. Karol BANDURSKI, Adiunkt</span><o:p></o:p></p><p class=MsoNormal><span style='mso-fareast-language:PL'>Wydział Inżynierii Środowiska i Energetyki</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:PL'>Zakład Ogrzewnictwa, Klimatyzacji i Ochrony Powietrza</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:PL'>Politechnika Poznańska</span><o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><span style='mso-fareast-language:PL'><br><br><o:p></o:p></span></p><pre>_______________________________________________<o:p></o:p></pre><pre>TRNSYS-users mailing list<o:p></o:p></pre><pre><a href="mailto:TRNSYS-users@lists.onebuilding.org">TRNSYS-users@lists.onebuilding.org</a><o:p></o:p></pre><pre><a href="http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org">http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org</a><o:p></o:p></pre></blockquote><pre>-- <o:p></o:p></pre><pre>***************************<o:p></o:p></pre><pre>David BRADLEY<o:p></o:p></pre><pre>Principal<o:p></o:p></pre><pre>Thermal Energy System Specialists, LLC<o:p></o:p></pre><pre>3 North Pinckney Street - suite 202<o:p></o:p></pre><pre>Madison, WI 53703 USA<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>P:+1.608.274.2577<o:p></o:p></pre><pre><a href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre><a href="http://www.tess-inc.com">http://www.tess-inc.com</a><o:p></o:p></pre><pre><a href="http://www.trnsys.com">http://www.trnsys.com</a><o:p></o:p></pre></div></body></html>